Unless they are both well-known to you before you submit your thesis, take some time in your viva prep to find out more about both your internal and your external.
- Ask friends and colleagues what they know of them. What work do they do? What are they known for?
- Explore their recent publications to get a sense of their interests and research focus. Is their work similar to yours or very different? Are there interesting connections between your areas?
- Talk to other academics about the role of the examiners. How do they approach the task? What do they look for in a good thesis?
Your examiners, whoever they are, are not just two random people. They are chosen for particular reasons. Explore that choice with your supervisors, explore your examiners’ work and explore the role of the examiner to well-prepared for meeting them in your viva.